Subsurface fluid-operated pump



March 13, 1962 c. ENGLISH 3,024,733

SUBSURF'ACE FLUID-OPERATED PUMP Filed March 18, 1960 2 Sheets-Sheet l g/llllllllllllll Mill IN VEN TOR. F E:-

CHAQLes La LLA/@UGH March 13, 1962 C. L. ENGUSH 3,024,733

SUBSURFACE FLUID-OPERATED PUMP Y dv/M United States Patent O 3,024,733SUBSURFACE FLUID-OPERATED PUMP Charles L. English, Tulsa, Okla. FiledMar. 18, 1960, Ser. No. 15,946 20 Claims. (Cl. 10B- 46) This inventionrelates generally to improvements in fluid-operated pump units such asare used in producing oil wells, and more particularly, but not by wayof limitation, to an improved fluid motor.

As it is well known in the oil producing industry, oil wells which haveceased flowing naturally are frequently produced by subsurfacefluid-operated pump units. The tluidoperated pump unit is supported inthe lower portion of an oil well and is energized by directing highpressure fluid, usually oil, from the surface downwardly through thewell bore to the engine or motor end of the pump unit. The pump unitoperates to force well fluids und exhausting power fluid upwardlythrough the well bore to the surface. Generally speaking, subsurfacefluidoperated pump units have performed satisfactorily and possessseveral distinct advantages over the more conventional sucker rod typepumps which are mechanically actuated by a surface power unit andrequire a string of rods extending from the surface of the welldownwardly to the subsurface pump. However, prior subsurface fluidoperated pumps have operated unsatisfactorily in some oil wells, whichhas prevented such pumps from being what may be considered universallyaccepted. For example, prior subsurface huid-operated pump units havefrequently operated unsatisfactorily in wells having a high gas-oilratio. ln such well conditions, the motor and pump pistons have atendency to move with excessive speeds, and most prior pump units failto make complete strokes in such gassy well conditions.

Most, if not all, present day subsurface Huid-operated pumps include anengine or motor piston assembly having a main valve therein whichcontrols the flow of high pressure uid to either one or both ends of themotor cylinder and opens an exhaust passageway from at least one end ofthe motor cylinder when power oil is being supplied to the opposite endof the motor cylinder. These main valves are of various designs, but arereciprocally disposed in the piston assembly for a shifting movement asthe piston assembly reaches or approaches the opposite ends of the motorcylinder. When the main valve is completely shifted from one of itsoperating positions to another, the flow of power oil and exhaustingpower oil is reversed to reverse the movement of the piston assembly. ltwill therefore be apparent that if the main valve is shifted prior tothe completion of a stroke of the piston assembly, the piston assemblywill still be immediately reversed. On the other hand, if the main valveis not shifted early enough, the piston assembly will tend to knockagainst the end of the motor cylinder and cause damage to the intricatepump construction. lt may be noted that if the main valve tends to shiftprior to the completion of the strokes of the piston assembly, the pumpend of the device tends to cavitate in gassy wells, that is. the pumpplunger will merely reciprocate in a gaseous medium and will not createsucient suction in the pump cylinder to draw in oil from the well bore.

Basically, two types of valve mechanisms have been used to shift themain valve as a piston assembly reaches the end of its stroke, as wellas hold the main valve in the desired position during a stroke of thepiston assembly. In one type of valve mechanism, a single pilot valveextends from one end of the piston assembly and is slidingly secured toone end of the motor cylinder, such that the pilot valve is mechanicallyshifted as the piston assembly reaches the end of either of its strokes.The pilot valve in turn controls the application of lluid pressures Cil3,024,733 Patented Mar. 13, 1962 on the main valve to hydraulicallyshift the main valve. When a single pilot valve of this type is used,the pilot valve is invariably subjected to varying Huid pressures, aswell as varying frictional forces, when the pump unit is subjected toabnormal operations, such as in gassy well conditions. These variousunpredictable forces on the pilot valve will frequently cause the pilotvalve to prematurely change position and provide a premature shifting ofthe main valve, such that the piston assembly merely oscillates throughan unduly short stroke length.

The other basic type of valve mechanism is exemplied in my co-pendingapplication entitled Oil Well Pump, led October 9. 1959, Serial No.845,571, now Patent No. 2,943,576. This latter type of Valve mechanismincludes only what may be considered a main valve which is physicallyunseated at the opposite ends of the movement of the piston assembly.but includes choking elements on the valve for controlling theapplication of fluid pressures to the valve after the valve is unseatedfor hydraulically shifting the valve from one operating position toanother. Such a valve mechanism is simple in construction and has beenfound exceptionally efcient in many operating environments. However, themechanical unseating of the valve possesses some inherent disadvantages.Since the amount of mechanical forces which can be applied to the valveis limited by the physical strength of the actuating members for thevalve. the force with which the main valve may be held on its operatingseats is also limited. Furthermore, the magnitude of the hydraulicforces imposed on the valve after it is unseated are also related to theforce with which the valve can be held on either of its seats. As aresult, any foreign matter which may become trapped between cooperatingsurfaces of the valve and the piston assembly will tend to hold thevalve in an intermediate and inoperative position. Also, the forcesapplied on the valve limit the speed with which the valve is shifted atthe end of a stroke of the piston assembly, such that the unseating ofthe valve must take place a short time prior to the end of a stroke.Therefore, under unusual operating conditions, the pump sometimes failsto move through its maximum stroke length, which reduces the overallefficiency of the pump unit.

The present invention contemplates a novel pump unit which may beutilized in substantially any pumping environment, The pump unitincludes a novel valve assembly comprising a main valve and two pilotvalves. One of the pilot valves controls the application of tluidpressure to the main valve at the end of one stroke of the unit and theother pilot valve controls the application of lluid pressure to the mainvalve at the end of the other stroke of the unit. Since each pilot valvehas only one operatingr position, the pilot valves may be easilyretained in their inoperative positions during the major portion of thecycle of operation of the unit and will not be affected by abnormalpressure conditions n the motor or engine end of the unit. Also, sincethe main valve is unseated and shifted solely by the application of huidpressures controlled by the pilot valves, the effective pressure areasof the main valve may be of sufficient size to securely hold the mainvalve in a desired operating position and to assure that the main valvewill be shifted from one operating position to another. Therefore, theoperation of the valve mechanism will be substantially unaffected eitherby foreign matter entering the unit, as by means of dirty power oil, orby varying pressure conditions in the motor end of the unit. ln apreferred construction, at least one of the pilot valves is in the formof a ball type valve which may be constructed of minimum size forcontrolling the application of maximum fluid pressures on the main valveand yet will have a minimum resistance against unseating as the pistonassembly reaches the end of astroke.

An important object of this invention is to provide a subsurfacehuid-operated pump unit which will operate efiiciently in substantiallyall environments.

Another object of this invention is to provide a subsurface uid-operatedpump unit which will not be rendered inoperative by a normal amount offoreign matter in the high pressure fluid used for operating the unit.

Another object of this invention is to provide a novel valve mechanismfor a lluid motor wherein the minimum force is required for actuatingthe pilot valves of the mechanism.

A further object of this invention is to provide a novel valve mechanismfor a lluid motor utilizing a main valve which will be held on itsoperating seats or in its operating positions with maximum forces andwill be shifted between its operating positions with the maximum forces.but wherein the minimum physical forces are imposed on the valvemechanism.

A more specific object of this invention is to provide a valve mechanismfor a fluid motor utilizing two pilot valves and wherein the pilotvalves will not be inadvertently shifted or actuated by abnormalpressure conditions in the motor.

A still further object `of this invention is to provide a subsurfacefluid-operated pump unit which is simple in construction, may beeconomically manufactured, may be easily repaired and which will have along service life.

Other objects and advantages of the invention will be evident from thefollowing detailed description, when read in conjunction with theaccompanying drawings which illustrate my invention.

In the drawings:

FIGURE lA is a vertical sectional view through the engine or motor endof a pump unit constructed in accordance with this invention.

FIGURE 1B is a continuation of the pump unit from the lower end of FIG.1A and is a vertical sectional view through the pump end of the unit.

FIGURE 2 is a vertical schematic sectional view through the engine endof the pump unit illustrating the position of the valve mechanism at theend of the downstroke of the unit.

FIGURE 3 is a view similar to FIG. 2 illustrating the position of thevalve mechanism at the beginning of the upstroke of the unit.

FIGURE 4 is another view similar to FIG. 2 illustrating the position ofthe valve mechanism during a normal upstroke ofthe unit.

FIGURE 5 is still another view similar to FIG. 2 illustrating theposition of the valve mechanism at the end of the upstroke of the pumpunit.

Referring to the drawings in detail, and particularly FIGS. 1A and IB,reference character 10 generally designates a pump unit constructed inaccordance with this invention and which generally comprises ahuid-operated motor 12 and a pump 14 connected to the lower end of thetluid motor in tandem relation with the Huid motor. The motor 12comprises a cylinder 16 having a cap or head 18 threadedly secured onthe upper end 20 thereof and having its lower end 22 threadedly securedin a counterborc 24 off a middle plug 26. The middle plug 26 forms thelower head for the motor cylinder 16 and the upper head for the pumpcylinder 28. It will be observed in FIG. lB that the upper end 30 of thepump cylinder 28 is threadedly secured in a counterbore 32 formed in thelower end of the middle plug 26.

A standing valve assembly, generally designated by reference character34, is secured on the lower end 36 of the pump cylinder 28 to controlthe flow of fluid from a well bore (not shown) into the lower end of themotor cylinder 28 in a manner common to the art. In this connection itmay also be noted that the pump unit is of a diametrical size forinsertion in a well bore at the level of the well fluid in the well borefor pumping this well fluid to the top of the well in a manner common tothe art. The standing valve assembly 34 comp-rises a tubular body 38having an upwardly facing valve seat 40 therein to receive a valvemember 42. The valve member 42 is provided with a stem 44 slidinglypositioned in a tubular guide 46 to retain the valve member 42concentric with the valve seat 40. The upward, opening movement of thevalve member 42 is limited by a suitable perforated stop 48. It will beapparent that the valve member 42 moves upwardly to `an open positionwhen the pressure in the lower end of the pump cylinder 28 is less thanthe pressure below the tubular standing valve body 38, and that thevalve member 42 will move downwardly to a closed position on the seat 40when the pressure in the lower end of the pump cylinder 28 is greaterthan the pressure below the valve member. Suitable threads 50 may beprovided in the lower end portion of the valve body 38, if desired, forsupporting a gas anchor (not shown) on the lower end of the pump unit 10in the usual fashion.

A tubular pump piston 52 is reciprocally disposed in the pump cylinder28 and is provided with a plurality of piston rings 54 around the outerperiphery thereof which slidingly and sealingly engage the innerperiphery of the pump cylinder 28 during reciprocation of the pumppiston. A seating member 56 is threadedly secured in the lower end ofthe pump piston 52 and is provided with an upwardly facing annularseating area 58 at the upper end thereof to receive a valve member 60.The valve member 60 is provided with a stem 62 extending downwardlytherefrom and slidingly received in a tubular guide 64 formed in thevalve seating member 56. It will therefore be apparent that the valvemember 60 moves upwardly when the pressure below the piston 52 is higherthan the pressure above the piston 52, and vice versa, such that thepump 14 is what is commonly known in the art as a single-acting pump. Itmay also be noted that the upstroke of the pump piston 52 is the workingstroke.

A hollow connecting rod 66 is connected to the upper end of the pumppiston S2 and extends vertically upward through the middle plug 26 intoconnection with the motor l2, as will be described. It should be notedhere, however, that the lower end 68 of the hollow connecting rod 66 isin communication with the interior of the piston S2 through a bore 70 toprovide a continuous passageway from the connecting rod 66 through theupper end portion of the piston 52 into the upper end portion of thepump cylinder 28.

Suitable packing 72 is retained in a bore 74 in the central portion ofthe middle plug 26 to provide a seal around the connecting rod 66. Thepacking 72 is held in fluid-tight engagement with the outer periphery ofthe connecting rod 66 and the walls of the bore 74 by a suitableretaining nut 76. An outlet 78 is formed through one side of the middleplug 26 below the packing 72 and in communication with the upper endportion of the pump cylinder 28. Therefore, all fluids pumped by thepump unit 14 will be discharged through the outlet 78. The outlet 78 inturn communicates with a suitable conduit (not shown) extending from thepump unit 10 upwardly to the top of the Well bore in which the pump unitis installed for recovery of the fluids pumped by the pump 14.

An inlet 80 (FIG. 1A) is also formed through one side of the middle plug26, but is positioned above the packing 72 to direct high pressure poweruid into the lower end of the motor cylinder 16 for operation of themotor 12, as will be described. It will be understood that the inlet 80communicates with a suitable conduit (not shown) extending from the topof the well bore in which the pump unit is installed, such that highpressure fluid may be pumped downwardly into the lower end of the pumpcylinder 16 for operation of the motor 12.

A motor piston assembly 82 is reciprocally disposed in the motorcylinder 16 and includes a piston element 84 having a plurality ofpiston rings 86 secured around the periphery thereof in sliding andsealing contact with the inner periphery of the cylinder 16. A piston extension 88 is threadedly secured to the lower end of the piston element84 and is in turn threadedly secured to the upper end 90 of the hollowconnecting rod 66. such that reciprocation of the motor piston assembly82 will be transferred to the pump piston 52. It may also be noted inthis connection that since the connecting rod 66 extends from the lowerend of the motor piston assembly 82, the downwardly facing areas of theassembly 82 are smaller than the upwardly facing areas of the pistonassembly, to provide what is commonly known in the art as a differentialarea piston.

A main valve chamber 92 is provided in the central portion of the pistonelement 84 and extends along the longitudinal center of the pistonelement 84 to be parallel with the direction of movement of the pistonassembly 82. A valve seating member 94 extends around a medial portionof the valve chamber 92 and is provided with an upwardly facing annularseating area 96 to receive a mating seating area 98 of the main valve100. The seating member 94 is provided with a suitable sealing ring 102around the periphery thereof and is held in operating position againstan upwardly facing shoulder 104 in the piston element 84 by an insert106 which is in turn held in the piston element by a cap member 108threadedly secured in the upper end of the piston element.

The main valve 100 is an elongated member of a size to provide ametal-to-metal seal with the walls of the medial portion of the valvechamber 92 and having sets of piston rings 110 and 112 on the lower andupper ends thereof, respectively. The lower piston rings 110 are securedaround the respective end of the valve 100 by suitable spacer rings 114which are in turn held in contact with one another and in Contact with adownwardly facing annular shoulder 116 by a suitable snap ring 118.These lower piston rings 110 form an enlarged head portion 119 whichslidingly contacts the walls of the lower, enlarged portion 120 of thevalve chamber 92.

A port 122 is formed transversely through the piston element 84 belowthe lower end of the main Valve 100 in communication with the enlargedportion 120 of the valve chamber 92 to form a portion of a high pressurepassageway through the piston assembly 82, as will be more fullyhereinafter set forth. A bore 124 extends longitudinally through themain valve 100 to provide a continuation of the high pressurepassageway. lt may also be noted that a small port or aperture 126 isformed transversely through the wall of the main valve 100 directlyabove the lower head portion 119 to provide communication between thevalve bore 124 and the enlarged portion 120 of the valve chamber 92, forpurposes to be described.

The upper piston rings 112 of the main valve 100 are supported in matinggrooves around an enlarged head portion 128 of the valve 100 toslidingly contact the walls of an upper enlarged portion 130 of thevalve chamber 92 formed by the spacer 106. lt will be observed that thedownwardly facing seating area 98 of the main valve 100 is formed aroundthe lower end portion of this head 128 to mate with the valve seat 94.

The medial portion 132 of the main valve 100 between the head 128 andthe main body portion of the valve which is slidingly sealed in thevalve chamber 92 is reduced in diameter to extend loosely through thevalve seat 94. This reduced diameter portion 132 is provided for thecommunication of ports 134 and 136 provided directly below and above thevalve seat 94 in one position of the valve 100, as will be described.The lower port 134 communicates with a passageway 138 extendingvertically through the piston element 84 and the piston extension 88.

The passageway 138 in turn communicates with the upper end of the hollowconnecting rod 66 through a suitable chamber 140 to form what may beconsidered an exhaust passageway which conducts spent operating or powerfluid from the upper end of the motor cylinder 16 downwardly into theconnecting rod 66. The uppcr port 136 extends through the spacer 106 andthe wall of the piston element 84 into communication with the Lipper endof the motor cylinder 16.

An upwardly facing annular seating arca 142 is formed at the upper endofthe main valve 100 around a counterbore formed at the upper end of thevalve bore 124 to mate with a downwardly facing seating area 146 formedon the cap member 108 at the upper end of the piston element 84. Theseating arca 146 is formed around a projection extending below the lowerend of the cup member 10S into a counterbore 148 formed in the upper endof the spacer 106. A plurality of ports 150 are formed in the cap member108 from the lower end thereof around the seating area 146 to a commonpassageway 152 com municating with the upper end of the cap member 108and the upper end portion of the motor cylinder 16. lt will he apparentthat when the main valve 100 is in the position shown in FIG. lA. thepassageway 152 and ports 150 communicate with the counterbore 148, the

valve bore 124, and the port 122 to form what is called herein the highpressure passageway, such that high pressure fluid may flow from thelower end portion of the motor cylinder 16 through the piston assembly82 into the upper end of the motor cylinder. In this connection it mayalso be noted that the low pressure or exhaust passageway 138 is closedbetween the ports 134 and 136 by the cooperation of the valve seatingareas 96 and 98. such that fluid may not be exhausted from the upper endportion of the motor cylinder 16 into the hollow connecting rod 66.

A ball type pilot valve 154 is positioned in a counterbore 156 formed inthe lower end of the cap member 108 concentrically inside of the seatingarea 146, The ball type valve 154 cooperates with a downwardly facingseating area 158 formed between the counterbore 156 and a bypass port160 which communicates with the passageway 152. lt will therefore beapparent that the ball pilot valve 154 will normally be retained on theseat 158 by the action of high pressure fluid in the upper end of thevalve bore 124 acting through the counterbore 156. The ball valve 154 isunseated by a rod 162 suitably secured to the upper cylinder head 118when the piston assembly 82 reaches the end of its upstroke. The rod 162has a reduced lower end portion 164 of a size to be received in thebypass port 160 to contact the ball valve 154 and physically unseat thisball valve. It may also be noted that a suitable retainer or spider 166is mounted in the counterbore 156 below the ball valve 154 to preventthe ball valve 154 from being completely removed from the counterbore156 when unseated by the rod 162. The stop 166 is perforated orotherwise suitably constructed so as not to interfere with the transferof fluid pressure therethrough against the ball valve 154.

Another pilot valve 168 is slidingly disposed in a tubular insert 170secured betweenthe piston element 84 and the piston extension 88 andextends through a bore 172 in the piston extension 88. The insert 170 issealed in the lower end of the enlarged portion 120 of the valve chamber 92 and in the piston extension 88 by suitable sealing rings 174 toprevent leakage from the lower end of the valve chamber. The pilot valve168 is an elongated member having a cylindrical head 176 formed on theupper end thereof and continuously exposed to the pressure of the fluidin the lower portion of the valve chamber 92A The head 176 is of a sizeto slidingly fit in the lower end of the main valve bore 124 to controlthe application of fluid pressure to the main valve at the lower end ofthe downstroke, as will be described. Also. a flange 178 extendsoutwardly around the pilot valve 168 directly below the head porti-on176 to limit the movement of the pilot valve into the main valve, aswill be described. A compression spring 180 extends around the pilotvalve 168 between the insert 170 and a nut 182 threaded onto the lowerend of the pilot valve, such that the spring 180 constantly urges thepilot valve 168 downwardly to move the cylindrical head portion 176 in adirection away from the main valve 100.

The pilot valve 168 is actuated by a suitable harness 184 when thepiston assembly 82 reaches the lower end of its downstroke. The harness184 comprises a ring 186 tting loosely around the piston extension 88arranged to contact an upwardly facing shoulder 188 at the lower end ofthe middle plug counterbore 24 when the piston assembly reaches the endof its downstroke. A bar 190 is secured to the upper end of the harnessring 186 by a suitable screw 192 and extends inwardly through a matingslot 194 in the piston extension 88 to contact the nut 182 on the lowerend of the pilot valve 168. lt will be apparent that when the harness184 contacts the upwardly facing shoulder 188 at the lower end of themotor cylinder 16, the pilot valve 168 will be moved upwardly relativeto the piston assembly upon any further downward movement of the pistonassembly. The harness 184 is normally in its lower position resting atthe lower end of the slot 194 by the action of gravity and, aspreviously noted, the spring 180 normally retains the pilot valve 168 inits lowermost position in contact with the harness 184 as illustrated inFIG. 1A.

Operation As previously indicated, high pressure power fluid, which isnormally in the form of clean oil, is continuously fed through the inlet80 into the lower end of the motor cylinder 16 to act on the downwardlyfacing areas of the piston assembly 82. ln the position of the mainvalve 100 shown in FlG. 1A, this high pressure power fluid also flowsthrough the port 122, the valve bore 124, the ports 150 and passageway152 to act on the upwardly facing areas of the piston assembly 82. Sincethe upwardly facing areas of the piston assembly 82 provide a largereffective area than the downwardly facing areas of the piston assembly'(by reason of the connecting rod 66 extending from the lower end of thepiston assembly), the net hydraulic force acting on the piston assembly82 will be in a downward direction to produce a downstroke for the pumpunit 10. During this downstroke it will also be observed that the pilotvalve 168 will be held in its lowermost position by the action of thespring 180 and by the action of gravity. The port 122 which provides theapplication of fluid pressure across the upper end of the lower pilotvalve 168 is of appreciable size and will produce no appreciablepressure drop for high pressure fluid flowing therethrough. Therefore,the fluid pressure forces acting on the pilot valve 168 will bebalanced, regardless of the speed of the downstroke or any othercommonly encountered abnormal pump operation, such that the pilot valve168 will remain in the position shown in FIG. 1A. The upper pilot valve1541's retained on its seat 158 by the action of high pressure fluidflowing through the valve bore 124 and through the upper end of thevalve chamber 92. However, on the downstroke of the pump unit, the powerfluid flows around the pilot valve 154 (through the ports 150) and it isimmaterial whether or not the pilot valve 154 is retained on its seat158.

Near the end of the downstroke of the pump unit, the harness 184contacts the upwardly facing shoulder 188 in the middle plug 26 (seeFIG. 2) and moves the lower pilot valve 168 upward relative to thepiston assem bly S2. As soon as the cylindrical head portion 176 of thepilot valve 168 first enters the lower end of the valve bore 124, flowof the power fluid through the valve bore 124 is restricted and asubstantial pressure drop occurs between the lower cntl of thc mainvalve chamber 92 and the valve bore 124 immediately above the pilotvalve cylindrical head 176. As a result, the cylindrical head 176 willbe sucked into the valve bore 124 to further restrict the flow of highpressure lluid into the valve bore 124. Since the piston assembly 82 ismoving downwardly at this time, the pressure of the fluid standing inthe valve bore 124, the upper end portion of the main valve chamber 92and in the upper end of the motor cylinder 16 is reduced to a pressurebelow the pressure of the power fluid. Thus, the force acting downwardlyon the upper end of the main valve and the force acting downwardly onthe lower head portion 119 of the main valve (by reason of the port 126)are reduced, while the upwardly acting force imposed by the power fluidon the lower head 119 of the main valve 100 is continued. As a result,the net force acting on the main valve 100 will be in an upwarddirection to shift the main valve 100 off of the seat 96 and onto theseat 146, as illustrated in FIG. 3.

ln analyzing the function of the valve mechanism at the end of thedownstroke, it will be apparent that the pilot valve 168 is first movedby physical contact with the harness 184, and then the upward movementof the pilot valve 168 is continued by hydraulic forces. As a result,the pilot valve 168 actually moves to a position above the harness 184when the cylindrical head portion 176 is fully inserted in the valvebore 124. It should also be noted that under the dynamic conditionsexisting during operation of the piston assembly 82, the lower pilotvalve 168 merely controls the application of fluid pressures on the mainvalve 100 and provides a hydraulic shifting of the main valve. Thehydraulic forces acting on the main valve 100 are changed immediatelyupon entry of the cylindrical head portion 176 into the lower end of thevalve bore 124 to initiate the shifting of the main valve. Thecylindrical head portion 176 will be moved on into the valve bore 124 byhydraulic forces until the flange 178 on the pilot valve 168 contactsthe lower end of the main valve. However, this physical contact takesplace after the hydraulic forces acting on the valve 100 are changed andactually does not function to shift the main valve. Since the pressureabove the cylin drical head portion 176 is then less than the upwardlyacting pressure forces on the pilot valve 168, the pilot valve 168 willtend to move upwardly with the main valve 100 against the action of thespring 180. As a result, some portion of the cylindrical head 176remains in the valve bore 124 during the complete shifting of the mainvalve from the seat 96 to the seat 146, such that the net hydraulicforce acting on the main valve 100 will continue to be in an upwarddirection while the main valve is fully seated on the seat 146. Thefinal position of the pilot valve 168 during a seating of the main valve100 on the seat 146 is illustrated in FIG. 3. As soon as the main valve100 is shifted to its upper position as shown in FIG. 3, the pilot valve168 is moved back downwardly by action of the spring 180 into contactwith the harness 184, as shown in FIG. 4.

When the lower pilot valve 168 is completely removed from the valve bole124, the power 'fluid has access to the valve bore 124 to act in anupward direction on the upper pilot valve 154 and positively close thebypass passageway 160. lt will be recalled that at this time thepressure above the piston assembly 82 is less than power fluid pressureand the pilot valve 154 will `be retained on its cooperating seat 158 bya pressure differential acting across the area of the seat 158. When themain valve 100 is seated on the seat 146 and when the bypass passageway160 is closed by the upper pilot valve 154, the hydraulic force actingdownwardly on the upper end of the main valve will be substantially lessthan the force acting upwardly across the lower end of the main valve.Also, power fluid is communicated through the port 126 across theupwardly facing area of the lower main valve head 119, but this area issmall compared with the downwardly facing lower end of the main valve,such that the main valve will be positively held on the upper seat 146during the upstroke of thc pump unit.

As the main valve 100 is being shifted upwardly and after the main valveis seated on the seat 146, the upward flow of power uid through thevalve bore 124 is discontinued and the exhaust passageway 138 isimmediately opened to provide a net hydraulic force on the pistonassembly 82 in an upward direction, such that the movement of the pistonassembly 82 is reversed and the pump unit moved on an upstroke. lt mayalso be noted that at the completion of the downstroke and during theshifting of the main valve 100, the lower end of the piston extension 88moves into a counterbore 200 formed in the middle plug 26 to provide adashpot action and further assure that the piston assembly 82 will notknock against the middle plug 26 and cause damage to the pump unit. Theslow reversal provided by this dashpot action and by fluid being fedinto the lower end of the motor cylinder 16 allows sutlicient time forthe pump traveling valve 60 to close, thus minimizing leakage throughthe pump piston 52 and increasing the service life of the travelingvalve seat 58.

During the upstroke of the pump unit, as shown in FIG. 4, uid in theupper end of the motor cylinder 16 is exhausted downwardly through thepassageway 138, as previously indicated, and this exhausting fluidenters the hollow connecting rod 66. Therefore, the exhausting powerfluid will be co-mingled with the well fluid being forced upwardlythrough the pump cylinder 28 by the action of the pump piston 52 andwill be discharged through the outlet 78 for conduction to the top ofthe well.

As the piston assembly 82 reaches the end of the upstroke, asillustrated in FIG. 5, the rod 162 is received in the passageway 152 andthe bypass 160 to Contact the upper ball type pilot valve 154. As aresult, the valve 154 is removed from its seat 158 to providecommunication from the valve bore 124 through the bypass 160 to theports 150 and increase the hydraulic force acting in a downwarddirection on the upper end of the main valve 100. This downwardly actingforce, in combination with the action of the power fluid across theupper end of the lower main valve head 119, provides a net downwardlyacting force on the main valve 100 to shift the main valve backdownwardly onto the seat 96 in the position illustrated in FIG. 1A. ltshould also be noted that the upwardly facing area of the upper end ofthe main valve 100 around the seating area 142 is substantially largerthan the cross sectional area of the pilot valve seat 158. Therefore,the mechanical force applied on the ball valve 154 by the rod 162 issubstantially less than the downwardly acting force obtained by theapplication of the power fluid through the bypass passageway 160 andports 150 against the upper end of the main valve. Furthermore, the ballvalve 154 and its cooperating seat 158 may be of minimum size tominimize the force required to be applied by the rod 162 to unseat thevalve` to in turn minimize the strength of materials required in thepump construction.

As soon as the main Valve 100 is shifted downwardly onto the seatingarea 96, the exhaust passageway 138 is closed and power fluid isadmitted to the upper end of the motor cylinder 16 through the valvebore 124, ports 150 and passageway 152 to again reverse the movement ofthe piston assembly 82 and provide a downstroke of the pump unit. lt mayalso be noted that since the rod 162 occupies an appreciable portion ofthe area of the passageway 152 at the end of the upstrok-e and thebeginning of the downstroke, the movement of the piston assembly 82 isslowly reversed and the standing valve 42 of the pump 14 will havesufficient time to close prior to the initiation of the downstroke, suchthat a minimum back-flow of well fluid downwardly from the pump cylinder23 through the standing valve assembly 34 will occur. This slow reversalof the pump stroke greatly facilitates the operation of the standingvalve 42 and minimizes the cutting out of the standing valve seat 40 bythe leakage of the dirty well uid therethrough.

ln analyzing the function of the Valve mechanism, it will be apparentthat both of the pilot valves 154 and 168 are mechanically actuated andthen control the application of fluid pressures on the main valve 1(10.The lower pilot valve 168 is actuated at the end of the downstroke toproduce a net hydraulic force on the main valve 190 in an upwarddirection to shift the main valve upwardly onto the seat 146. At the endof the upstroke` the pilot valve 154 is mechanically actuated by the rod162 to produce a net hydraulic force on the main valve ltl acting in adownward direction to move the main valve downwardly onto the seatingarea 96. Since the main valve 100 is both unseated and then shiftedsolely by hydraulic forces, the pressure areas of the main valve may bedesigned to provide substantial hydraulic forces for unseating thevalve, shifting the valve and holding the valve on its respective seats.Furthermore, the pressure areas of the main valve 100, and the actualforces applied on the main valve for the unseating, shifting and holdingoperations are not limited by either the sizes or strengths of the pilotvalves. The upper pilot valve 154 and the actuating rod 162 may be ofeconomical construction, since the only force applied on the pilot valve154 is that force necessary to overcome a pressure differential actingacross the area of the pilot valve seat 158. The mechanical unseating ofthe ball valve 154 results in a substantial hydraulic force benigapplied to the main valve 100. The lower pilot valve 168 is movedmechanically only against the action of the spring 1.80, such that theharness 184 will have minimum strength requirements. Here again, themechanical force applied to the lower pilot valve 168 is extremely smallcompared with the resulting hydraulic forces imposed on the main valve100 for the unseating, shifting and holding of the main valve.

The above-described functional requirements for the pilot valves 154 and168 not only provide an economical construction having minimum strengthrequirements, but also assure that the piston assembly 82 will completeits up and down strokes under substantially all operating conditions.The appreciable hydraulic forces imposed on the main valve 100 willminimize the possibility of the main valve being stuck in an inoperativeposition by the accumulation of foreign matter from dirty power fluid inthe valve chamber 92. Also, since substantial hydraulic forces areimposed on the main valve by minimal physical actuation of the pilotvalves 154 and 168, the actuating mechanisms comprising the rod 162 andthe harness 134 may be designed to provide a shift of the main valve 100only when each stroke of the piston assembly 82 is substantiallycomplete. In other words, the valve mechanism and the actuators 162 and184 may be designed to shift the main valve when the piston assembly 82is within a few thousandths of an inch from the respective end of themotor cylinder 16. The fast response of the main valve 100 to theapplication of the hydraulic forces provides an immediate control of theflow of the power fluid to the piston assembly 82 to reverse the pistonassembly movements. As a result, the present pump unit will beparticularly effective under abnormal operating conditions, such as whenthe pump unit is used in gassy wells or is driven by dirty power fluid,to provide a pump unit having universal utility.

From the foregoing it will be apparent that the present inventionprovides a novel subsurface fluid-operated pump unit which is simple inconstruction, may be economically manufactured, may be easily repairedand which will have a long service life. The present pump unit will havesubstantially more universal utility than present-day subsurfacefluid-operated pumps. The pump unit will not tend to cavitate in gassywell conditions and each stroke of the pump unit will be completedbefore the next stroke is undertaken to assure the maximum efficiency ina pumping operation. Also, the reversals of the pump unit will beretarded such that the valves in the pump end of the unit will have themaximum service life. The valve mechanism of the motor end of the unitis simply constructed, will not be affected by abnormal pumpingconditions and may be economically constructed.

Changes may be made in the combination and arrangement of parts orelements as heretofore set forth in the specification and shown in thedrawings, it being understood that changes may be made in the preciseembodiment disclosed herein without departing from the spirit and scopeof the invention as defined in the following claims.

I claim:

l. A subsurface fluid-operated pump unit, comprising: a motor cylindermember; a motor piston member reciprocally disposed in the motorcylinder member and responsive to fluid pressures in the opposite endsof the motor cylinder member for reciprocation in the motor cylindermember; a main valve chamber in one of said members; a high pressurepassageway intersecting the main valve chamber and communicating with atleast one end of the motor cylinder member; an exhaust passagewayintersecting the main valve chamber and communicating with at least oneend of the motor cylinder member; valve seats in the main valve chamberin the high pressure and exhaust passageways; a main valve disposed inthe main valve chamber and being responsive to the application of fluidpressures thereto for reciprocation in the main valve chamber toalternately seat on the valve seats and control the flow of fluid to andfrom at least one end of the motor cylinder member; a pair of pilotvalves in the high pressure passageway for controlling the applicationof high pressure fluid to the main valve for shifting the main valve offof and on to said seats; separate actuating means at the opposite endsof one of said members arranged to actuate one of the pilot valves whenthe motor piston member reaches one end of the motor cylinder member andactuate the other pilot valve when the motor piston member reaches theopposite end of the motor cylinder member; a pump cylinder connected intandem relation to the motor cylinder member and having an inlet and anoutlet, and a pump piston reciprocally disposed in the pump cylinder andconnected to the motor piston member.

2 A subsurface fluid-operated pump unit as defined in claim l whereinone of said pilot valves comprises a ball type valve and cooperatingseat with the seat facing high pressure fluid in the high pressurepassageway such that the ball type valve is continuously urged onto theseat by the high pressure fluid, one of said actuating means comprises arod positioned to knock said ball type valve off of its cooperating seatwhen the motor piston member reaches the respective end of the motorcylinder member, and characterized further to include a bypasspassageway extending from said ball type valve seat to the main valvechamber for applying high pressure fluid against the main valve when theball type valve is removed from its seat.

3. A subsurface fluid-operated pump unit as defined in claim l whereinsaid main and pilot valves are carried by the motor piston member inalignment along the axis of movement of the motor piston member, andsaid main valve is tubular in form with the bore therethrough forming aportion of said high pressure passageway.

4. A subsurface fluid-operated pump unit as defined in claim 3 whereinthe main valve chamber is elongated, said pilot valves are positioned atthe opposite ends of the main valve chamber, one of said pilot valvescom prises a ball valve seat facing the opposite end of the main valvechamber and a ball type valve cooperating with said ball valve seat, oneof the seats for the main valve comprises an annular seating areaarranged concentrically around said ball valve seat to receive therespective end of the main valve, and characterized further to include abypass passageway from said ball type valve seat around said concentricmain valve seat for directing high pressure fluid against the respectiveend of the main valve when the main valve is seated on said concentricseat and said ball type valve is actuated.

5. A subsurface fluid-operated pump unit as defined in claim 4 whereinthe other of said pilot valves comprises an elongated elementreciprocally supported in the motor piston member with one end thereofprojecting into the main valve chamber, said one end of said other pilotvalve being in the form of a cylindrical head of a size to slidingly litthe adjacent end of the main valve, and one of said actuating meanscomprises a harness carried by the motor piston member in a position tocontact said other pilot valve and move said cylindrical head into theadjacent end of the main valve and control the application of fluidpressure on the main valve when the motor piston member reaches one endof the motor cylinder member.

6. A subsurface fluid-operated pump unit, comprising: a motor cylinder;a motor piston assembly reciprocally disposed in the motor cylinder andhaving a large end and a small end; a supply of high pressure powerfluid; means providing constant communication between said supply andthe end of the motor cylinder associated with the small end of the motorpiston assembly to constantly ar ply power fluid against said small endand urge the motor piston assembly in one direction in the motorcylinder; a main valve chamber in the motor piston assembly; a firstpassageway intersecting the main valve chamber providing communicationbetween said supply and the end of the motor cylinder associated withthe large end of the motor piston assembly to direct power fluid againstthe large end of the rnc-tor piston 'assembly and urge the motor pistonassembly in an opposite direction; an exhaust passageway intersectingthe main valve chamber and communicating with the end of the motorcylinder associated with the large end of the motor piston assembly forexhausting power fluid from the end of the motor cylinder associated bythe large end of the motor piston assembly and provide movement of themotor piston assembly in said one direction; a valve seat in the mainvalve chamber in each of the first and exhaust passageways, said valveseats being positioned in spaced relation; a main valve reciprocallydisposed in the main valve chamber for alternately closing said valveseats and controlling the flow of power fluid to and from the end of themotor cylinder associated with the large end of the motor pistonassembly; a first pilot valve carried by the motor piston assembly andcooperating with said first passageway to control the ap-plication ofpower fluid pressure to the main valve and hydraulically shift the mainvalve from one of said seats to the other seat; a second pilot valvecarried by the motor piston assembly and cooperating with said firstpassageway to control the application of power fluid pressure to themain valve and hydraulically shift the main valve from said other valveseat to said one valve seat; means for actuating one of said pilotvalves when the motor piston assembly reaches one end of the motorcylinder; separate means for actuating the other of said pilot valveswhen the motor piston assembly reaches the opposite end of the motorcylinder; a pump cylinder connected in tandem relation to the motorcylinder and having a fluid inlet and outlet; a pump piston assemblyreciprocally disposed in the pump cylinder, and a connecting rod securedto the pump piston assembly and the motor piston asssembly toreciprocate the pump piston assembly simultaneously with the motorpiston assembly.

7. A subsurface fluid-operated pump unit as defined in claim 6 whereinthe main valve chamber is an elongated chamber extending along the axisof movement of the motor piston assembly, said main valve is tubular inform and the bore therethrough forms a portion of Said first passageway,and said pilot valves are positioned at the opposite ends of the mainvalve chamber.

S. A subsurface fluid-operated pump unit as defined in claim 7 whereinone of said pilot valves comprises a ball valve seat facing the oppositeend ofthe main valve chamber and a ball type valve cooperating with saidseat, one of said main valve seats comprises an annular seating areapositioned at the end of the main valve chamber associated with the ballvalve and arranged concentric'ally around said ball valve seat, saidmain valve having a seating area around the inner periphery of the endthereof associated with the ball type valve to mate with said annularseating area in one position of the main valve, a bypass passagewayextending from said ball valve seat, and said first passageway beingextended from said bypass passageway around said annular seating area tapply high pressure fluid pressure on the end of the main valve when themain valve is seated on said annular seating area and said ball valveseat is open.

9. A subsurface fluid-operated pump unit as defined in claim 7 whereinone of' said pilot Valves comprises an elongated element reciprocallysupported in the motor piston `assembly in alignment with the main valveand with the opposite ends thereof exposed to said high pressure fluid,one end of said elongated element being positioned in the respective endof the main valve chamber, said one end of said elongated element beingin the form of a cylindrical head of a size to slidingly fit in therespective end of the main valve, and said actuating means associatedwith said elongated element comprises a harness carried by the motorpiston assembly in a position to contact one end of the motor cylinderwhen the motor piston assembly reaches said end for contacting saidelongated element and moving said cylindrical head into the respectiveend of the main valve for controlling the application of fluid pressureon the main valve.

l0. A reciprocating type fluid motor, comprising a cylinder member; apiston member reciprocally disposed in the cylinder member andresponsive to fluid pressures in the opposite ends of the cylindermember for reciprocation in the cylinder member; a main valve chamber inone of said members; a high pressure passageway intersecting the mainvalve chamber and communicating with at least one end of the cylindermember; an exhaust passageway intersecting the main valve chamber andcommunicating with at least one end of the cylinder member; valve seatsin the main valve chamber in the high pressure and exhaust passageways;a main valve disposed in the main valve chamber and being responsive tothe application of fluid pressure thereto for reciprocation in the mainvalve chamber to alternately seat on the valve seats and control theflow of fluid to and from at least one end of the cylinder member; apair of pilot valves in the high pressure passageway for controlling theapplication of high pressure fluid to the main valve for shifting themain valve off of and onto said seats; and separate actuating means atthe opposite ends of one of said members arranged to actuate one of thepilot valves when the piston member reaches one end of the cylindermember and actuate the other pilot valve when the piston member reachesthe opposite end of the cylinder member.

ll. A fluid motor as defined in claim 10 wherein one of said pilotvalves comprises a ball type valve and cooperating seat with the seatfacing high pressure fluid in the high pressure passageway such that theball type valve is continuously urged onto the seat by high pressurefluid, one of said actuating means comprises a rod positioned to knockthe ball type pilot valve ofi of its cooperating seat when the pistonmember reaches the respective end of the cylinder member, andcharacterized further to include a bypass passageway extending from saidball type valve seat to the main valve chamber for applying highpressure fluid against the main valve when the ball type valve isremoved from its seat.

l2. A fluid motor as defined in claim 10 wherein said main valve istubular in form and the bore therethrough forms a portion of the highpressure passageway, one of said pilot valves includes a cylindricalhead of a size to slidingly fit in one end of the main valve, saidlast-mentioned pilot valve being reciprocally supported in alignmentwith and adjacent to one end of the main valve for movement of saidcylindrical head into the main valve upon actuation thereof by one ofsaid actuating means to control the application of fluid pressure on themain valve and shift the main valve, and characterized further toinclude a spring anchored to said last-mentioned pilot valve urging saidpilot valve in a direction away from the main valve.

f3. A fluid motor as defined in claim 10 wherein said main and pilotvalves are carried by the piston member in alignment along the axis ofmovement of the piston mem.- ber, and said main valve is tubular in formwith the bore therethrough forming a portion of said high pressurepassageway.

14. A fluid motor as defined in claim 13 wherein the main valve chamberis elongated, said pilot valves are positioned at the opposite ends ofthe main valve chamber, one of said pilot valves comprises a ball valveseat facing the opposite end of the main valve chamber and a ball typevalve cooperating with said ball valve seat, one of the seats for themain valve comprises an annular seating area arranged concentricallyaround said ball valve seat to receive a seating area formed on therespective end of the main valve, said last-mentioned seating area beingformed around the inner periphery of the main valve, and characterizedfurther to include a bypass passageway from said ball type valve seataround said concentric main valve seat for directing high pressure fluidagainst the respective end of the main valve when the main valve isseated on said concentric seat and said ball type valve is actuated.

l5. A fluid motor as defined in claim 14 wherein the other of said pilotvalves comprises an elongated element reciprocally supported in thepiston member with one end thereof projecting into the main valvechamber, said one end of said other pilot valve being in the form of acylindrical head of a size to slidingly fit in the adjacent end of themain valve, and one of said actuating means comprises a harness carriedby the piston member in a position to contact said other pilot valve andmove said cylindrical head into the adjacent end of the main valve andcontrol the application of fluid pressure on the main valve when thepiston member reaches one end of the cylinder member.

16. A reciprocating type fluid motor, comprising: a cylinder; a pistonassembly reciprocally disposed in the cylinder and having a large endand a small end; a supply of high pressure power fluid; means providingconstant communication between Said supply and the end of the cylinderassociated with the small end of the piston assembly to constantlysupply power fluid against said small end and urge the piston assemblyin one direction in the cylinder; a main valve chamber in the pistonassembly; a first passageway intersecting the main valve chamberproviding communication between said supply and the end of the cylinderassociated with the larger end of the piston assembly to direct powerfluid against the large end of the piston assembly and urge the pistonassembly in an opposite direction; an exhaust passageway intersectingthe main valve chamber and communicating with the end of the cylinderassociated with the large end of the piston assembly for exhaustingpower fluid from the end of the cylinder associated with the large endof the piston assembly and provide movement of the piston assembly insaid one direction; a valve seat in the main valve chamber in each ofthe first and exhaust passageways, said valve seats being positioned inspaced relation; a main valve reciprocally disposed in the main valvechamber for alternately closing said valve seats and controlling theflow of power fluid to and from the end of the cylinder associated withthe large end of the piston assembly; a rst pilot valve carried by thepiston assembly and cooperating with said first passageway to controlthe application of power fiuid pressure to the main valve andhydraulically shift the main valve from one of said seats to the otherseat; a second pilot valve carried by the piston assembly andcooperating with said first passageway to control the application ofpower iiuid pressure to the main valve and hydraulically shift the mainvalve from said other valve seat to said one valve seat, means foractuating one of said pilot valves when the piston assembly reaches oneend of the cylinder, and separate means for actuating the other of saidpilot valves when the piston assembly reaches the opposite end of thecylinder.

17. A uid motor as defined in claim i6 wherein said main valve chamberis an elongated chamber extending along the axis of movement of thepiston assembly, said main valve is tubular in form and the boretherethrough forms a portion of said first passageway, and said pilotvalves are positioned at the opposite ends of the main valve chamber.

18. A uid motor as defined in claim 17 wherein one of said pilot valvescomprises a ball valve seat facing the opposite end of the main valvechamber and a ball valve cooperating with said seat, one of said mainvalve seats comprises an annular seating area positioned at the end ofthe main valve chamber associated with the ball valve and arrangedconcentrically around said ball valve seat, said main valve having aseating area around the inner periphery of the end thereof facing theball type valve to mate with said annular seating area in one positionof the main valve. a bypass passageway extending from said ball valveseat, and said first passageway being extended from bypass passagewayaround said annular seating area to apply high pressure fluid pressureon the respective end of the main valve when the main valve is seated onsaid annular seating area and said ball valve seat is open.

i9. A fluid motor as defined in claim 18 wherein said actuating meansassociated with said ball type valve comprises a rod secured to therespective end of the cylinder and being of a size to be received insaid first passageway when the piston assembly reaches the respectiveend of the cylinder for unseating said ball type valve from itscooperating seat.

20. A fluid motor as defined in claim 17 wherein one of said pilotvalves comprises an elongated element reciprocally Supported in thepiston assembly in alignment with the main valve and with the oppositeends thereof exposed to said high pressure uld, one end of saidelongated element being positioned in the respective end of the mainvalve chamber, said one end of said elongated element being in the formof a cylindrical head of a size to slidingly fit in the respective endof the main valve` and Said actuating means associated with saidelongated element comprising a harness carried by the piston assembly ina position to contact one end of the cylinder when the piston assemblyreaches said end for contacting said elongated element and moving saidcylindrical head into the respective end of the main valve forcontrolling the application of uid pressure on the main valve.

References Cited in the file of this patent UNITED STATES PATENTS2,183,538 Butler Dec. 19, i939 2,580,657 Coberly Jan. l, 1952 2,746,431Tebbetts May 22, 1956 2,821,141 Sargent Jan. 28, 1958

